I'm new to fountains and enjoy my Lamy Safari even if it is inexpensive plastic. The refillable reservoir is of the screw-suction type but I don't use it that way. I use an inexpensive syringe to transfer ink.
If I ever use a disposable cartridge again I'll try reusing it instead.
Do use luer-lock though, because the other kind of syringes suck. Just ask your local pharmacy -- they usually carry them and they can be used for all sorts of non-illicit-drug reasons.
In the US/Canada Lee Valley sells a set of blunt tip syringes for inks and glues.